The present invention relates generally to closure arrangements for containers and more particularly to a closure or cap arrangement for a fuel container which provides venting to the fuel reservoir while reducing fuel expulsion from the reservoir by way of that venting arrangement.
When fuel is drained from a fuel reservoir, the fuel volume within that reservoir diminishes and unless another medium, such as air is supplied to the reservoir to occupy the vacated space, the supply of fuel is inhibited or in some cases collapsing of the reservoir occurs. For example, with a small fuel tank as might be found on a gasoline powered lawnmower, snowblower, or the like, the fuel tank screw-on filler cap is typically provided with a small aperture for venting the tank to allow air to enter and occupy space previously occupied by the consumed fuel. While this simple venting arrangement is generally adequate, it does have several, sometimes dangerous, drawbacks. If the fuel tank is inadvertently inverted, fuel may drain out the venting aperture, creating a fire hazard. Even when the tank is in its normal attitude with the filler cap near the top thereof when the reservoir is completely filled with fuel, some fuel may be expelled through the venting aperture, for example due to expansion of the fuel when subjected to elevated temperatures, or fuel may on occasion spit from the venting aperture due to vibration of the tank or due to flexing of the tank side walls causing a temporary diminution of the tank volume.
Several prior art techniques have addressed the problem of the inadvertent expulsion of fuel from the fuel tank venting arrangement. For example, automotive fuel tanks have been provided with filler caps having a check valve in the fuel tank cap venting arrangement which check valve allows air to enter the tank but tends to close to prevent air or fuel from leaving the tank. Such a fuel tank cap is illustrated, for example, in U.S. Pat. No. 2,800,245 to Doyle et al.
Other prior art fuel tank caps have attempted to provide venting without fuel seapage by providing a series of baffles within the cap so that the air flow route into the cap is a serpentine path with no direct flow path from the cap vent hole into the tank. Typical of this approach is U.S. Pat. No. 3,140,794 to Arndt et al. There have been other generally more complex attempts at fuel tank venting arrangements but none have met with any significant commercial success. This lack of success may be traced to either excessive complexity and cost of the venting arrangement of failure of the venting arrangement to provide the desired results.
While the present invention may find use in a wide variety of environments it is especially suited to vented cap arrangements for fuel supply reservoirs associated with small internal combustion engines where simplicity and economy are key notes.
In the exemplary small internal combustion engine fuel reservoir environment, spitting or spurting of fuel from the fuel cap vent is frequently a direct result of fuel becoming trapped between baffles in that fuel cap and the cap vent hole. This trapping of fuel in turn has two frequent causes. If the fuel tank is full or nearly full, and then the fuel temperature increases, the fuel volume also increases, causing an overflow condition. The increase in fuel temperature may occur while the engine is running but be sufficient that the expansion rate exceeds the rate at which fuel is consumed by the engine. Another frequent cause of fuel being trapped in fuel cap baffling is "oil canning" of the fuel tank during engine operation. This flexing of the fuel tank walls creates a pumping action which, particularly when the tank is full or nearly full of fuel, forces fuel into the cap. Once baffle regions in the cap contain fuel, any additional pumping forces fuel to spurt out of the fuel cap vent opening with the severity of fuel spitting being a function of how full the tank is and how intensely it vibrates.
One attempt at preventing the spurting of fuel from the reservoir through the filler cap vent hole was to try to keep the fuel tank from vibrating, however, in the exemplary small internal combustion engine environment such tank vibration damping would require major modification to the tank and engine arrangement and would increase the cost of the assembly prohibitively.